Subject: Re: RMNET QMAP data aggregation with size greater than 16384

From: [email-masked]
Date: Mon, 09 Aug 2021 15:40:41 -0600

> No need for () around a constant, is there?
> 
> Either I'm blind, or you don't actuelly change the rx_urb_size for the
> mux and pass through modes?
> 

I seem to have missed this and the other stuff you have pointed out.
Can you please review this update-

> 
> I'd also prefer this to reset back to syncing with hard_mtu if/when
> muxing or passthrough is disabled.  Calling usbnet_change_mtu() won't 
> do
> that. It doesn't touch rx_urb_size if it is different from hard_mtu.
> 
> I also think that it might be useful to keep the mtu/hard_mtu control,
> wouldn't it?
> 
> 
> Something like
> 
>    old_rx_urb_size = dev->rx_urb_size;
>    if (mux|passthrough)
>        dev->rx_urb_size = MAP_DL_URB_SIZE;
>    else
>        dev->rx_urb_size = dev->hard_mtu;
>    if (dev->rx_urb_size > old_rx_urb_size)
>        unlink_urbs etc;
>    return usbnet_change_mtu(net, new_mtu);
> 
> should do that, I think.  Completely untested....
> 
> And add it to the (!qmimux_has_slaves(dev)) cas in del_mux_store() too.
> 

Assuming this patch doesn't have too many other issues, can I request
Aleksander / Daniele to try this out.

diff --git a/drivers/net/usb/qmi_wwan.c b/drivers/net/usb/qmi_wwan.c
index 6a2e4f8..4676544 100644
--- a/drivers/net/usb/qmi_wwan.c
+++ b/drivers/net/usb/qmi_wwan.c
@@ -75,6 +75,8 @@ struct qmimux_priv {
         u8 mux_id;
  };

+#define MAP_DL_URB_SIZE 32768
+
  static int qmimux_open(struct net_device *dev)
  {
         struct qmimux_priv *priv = netdev_priv(dev);
@@ -303,6 +305,39 @@ static void qmimux_unregister_device(struct 
net_device *dev,
         dev_put(real_dev);
  }

+static int qmi_wwan_change_mtu(struct net_device *net, int new_mtu)
+{
+       struct usbnet *dev = netdev_priv(net);
+       struct qmi_wwan_state *info = (void *)&dev->data;
+       int old_rx_urb_size = dev->rx_urb_size;
+
+       /* mux and pass through modes use a fixed rx_urb_size and the 
value
+        * is independent of mtu
+        */
+       if (info->flags & (QMI_WWAN_FLAG_MUX | 
QMI_WWAN_FLAG_PASS_THROUGH)) {
+               if (old_rx_urb_size == MAP_DL_URB_SIZE)
+                       return 0;
+
+               if (old_rx_urb_size < MAP_DL_URB_SIZE) {
+                       dev->rx_urb_size = MAP_DL_URB_SIZE;
+
+                       usbnet_pause_rx(dev);
+                       usbnet_unlink_rx_urbs(dev);
+                       usbnet_resume_rx(dev);
+                       usbnet_update_max_qlen(dev);
+               }
+
+               return 0;
+       }
+
+       /* rawip mode uses existing logic of setting rx_urb_size based 
on mtu.
+        * rx_urb_size will be updated within usbnet_change_mtu only if 
it is
+        * equal to existing hard_mtu
+        */
+       dev->rx_urb_size = dev->hard_mtu;
+       return usbnet_change_mtu(net, new_mtu);
+}
+
  static void qmi_wwan_netdev_setup(struct net_device *net)
  {
         struct usbnet *dev = netdev_priv(net);
@@ -326,7 +361,7 @@ static void qmi_wwan_netdev_setup(struct net_device 
*net)
         }

         /* recalculate buffers after changing hard_header_len */
-       usbnet_change_mtu(net, net->mtu);
+       qmi_wwan_change_mtu(net, net->mtu);
  }

  static ssize_t raw_ip_show(struct device *d, struct device_attribute 
*attr, char *buf)
@@ -433,6 +468,7 @@ static ssize_t add_mux_store(struct device *d,  
struct device_attribute *attr, c
         if (!ret) {
                 info->flags |= QMI_WWAN_FLAG_MUX;
                 ret = len;
+               qmi_wwan_change_mtu(dev->net, dev->net->mtu);
         }
  err:
         rtnl_unlock();
@@ -466,8 +502,11 @@ static ssize_t del_mux_store(struct device *d,  
struct device_attribute *attr, c
         }
         qmimux_unregister_device(del_dev, NULL);

-       if (!qmimux_has_slaves(dev))
+       if (!qmimux_has_slaves(dev)) {
                 info->flags &= ~QMI_WWAN_FLAG_MUX;
+               qmi_wwan_change_mtu(dev->net, dev->net->mtu);
+       }
+
         ret = len;
  err:
         rtnl_unlock();
@@ -514,6 +553,8 @@ static ssize_t pass_through_store(struct device *d,
         else
                 info->flags &= ~QMI_WWAN_FLAG_PASS_THROUGH;

+       qmi_wwan_change_mtu(dev->net, dev->net->mtu);
+
         return len;
  }

@@ -643,7 +684,7 @@ static const struct net_device_ops 
qmi_wwan_netdev_ops = {
         .ndo_stop               = usbnet_stop,
         .ndo_start_xmit         = usbnet_start_xmit,
         .ndo_tx_timeout         = usbnet_tx_timeout,
-       .ndo_change_mtu         = usbnet_change_mtu,
+       .ndo_change_mtu         = qmi_wwan_change_mtu,
         .ndo_get_stats64        = dev_get_tstats64,
         .ndo_set_mac_address    = qmi_wwan_mac_addr,
         .ndo_validate_addr      = eth_validate_addr,